Key circuit for tube senders



. v ,64 ,5 7 Oct. 25.1927. w. ZELETZK| I 1 51 KEY cmcuu' FOR TUBE SENDERS Filed March 26. 1923 Patented Oct. 25, "1 927 UNITED STATES PATENT oF' icE.

WILLY ZELETZKI, or BERLIN, GERMANY, ASSIGNOR T0 GESELLSCHAFT rim meanw- LO SE TELEGRAPHIE IVL' B. H. HALLESCI-IES, OF BERLIN, GERMANY, A COEIORA TION, OF GERMANY.

KEY CIRCUIT non TUBE SENDERS.

Application filed March 26, 1923, Serial No. 627,576, and in Germany April 19, 1922 The usual method of controlling the grid of a tube generator circuit by means of a key consists in interrupting the grid conductor, i. e. the high frequency pathand the path through which the grid .direct current is discharged in rhythm with the operation of the key. As is well known, it is also pos-' sible to leave the high frequency path undisturbed and to control by means of the key only the direct current discharge path of the grid.

The condenser has heretofore been so proportioned that the drop of high frequency potential is very slight. In order to accomplish this, the condenser may be relatively small (.a few thousand cm.) because the high frequency current, flowing therethrough is very small. When the grid circuit is interrupted by the key, the oscillations generated by the tube in the oscillating circuit will cease but the normal current will continue to flow through the tube, due to which, under certain circumstances, even larger losses may be caused in the tube than'during the oscillating condition. ,This is particularly the case when the direct current potential in the plate circuit of a tube is mate.- rially increased upon the interruption of the grid circuit by the key so that the plate cur-v rent tendsto be much higher in the normal condition than it would be if the voltage of the plate current source did not increase 7 v with decrease in current drain.

For the purpose of eliminating or reducing as far as possible the normal current flowing through the tube during the resting condition, it has been suggested to provide a separate source of current which upon the opening of the key applies a negative potential to the grid of the tube. However, the

The latter is usually accomplished by pro in series 7 circuit arrangement proposed for this pur-- pose is complicated because a separate source r.

creasing the condenser which is connected in parallel with the key out of. proportion,

often 50 or times or more, with the size necessary to maintain the drop of the high frequency potential in the grid circuit at the slight degree-required, the normal current flowing through the tube may be so reduced as to be approximately equal to zero without the' provision of a separate battery.

The same result may be attained by a combination consisting'of a veryhigh resistance in parallel with the condenser.

In the drawing,

Fig. 1 is a diagrammatic representation of a circuit arrangement embodying the invention and fig. 2 is a diagrammatic representation of 'a modified form of the invention.

The illustrated construction comprisesa three-electrode vacuum tube '2 having a grid 4 and a grid-filament circuit 6. Arranged in series in the grid-filament circuit are akey 8 and a choke-coil 10, and connected in parallel with the key Sand the choke-coil 10 1s a condenser 12' ofa capacity many times,

for example, 50 or 100" times, larger than that required to maintain-the drop of high frequency potential in the grid-filament circuit at the required small degree. i

As shown in Fig. 2, a very high resistance 14 is arranged in parallel withthc condenser 12 for the purpose of'preventing losses. in

the tube while the key is open by reducing the current in the tube at such times approximately to zero.

Having described my invention, what I claim is: I 1 q A circuit arrangement for tube generators comprising a three-electrode vacuum tube, a grid-filament circuit for said tube, a key and a choke coil arranged in series in the gridfilament circuit, a condenser connected in" parallel with the key and chokecoil, and a high resistance connected in parallel with the condenser. I WILLY ZELETZKI. 

